The designer shouldn't think of a simple dichotomy between errors and correct behavior; rather, the entire interaction should be treated as a cooperative endeavor between person and machine, one in which misconceptions can arise on either side.
Donald A. NormanI think there is a tendency in science to measure what is measurable and to decide that what you cannot measure must be uninteresting.
Donald A. NormanAny time you see signs or labels added to a device, it is an indication of bad design: a simple lock should not require instructions.
Donald A. NormanUser experience is really the whole totality. Opening the package good example. It's the total experience that matters. And that starts from when you first hear about a product experience is more based upon memory than reality. If your memory of the product is wonderful, you will excuse all sorts of incidental things.
Donald A. Norman